Process for producing esters of acrylic acid



Patented Oct. 17, 1950 UNITED STATES TENT OFFICE PROCESS FOR. PRODUCING ESTERS or ACRYLIC ACID N Drawing. Application February 1 8, 1947, Serial No. 729,414

.10'ClaimS- 260-486);

This invention relates to the production of which the mixture is maintained so that the methyl, ethyl and propyl esters of acrylic acid from acrylonitrile and methyl, ethyl or propyl alcohol.

It is known that many aliphatic and aromatic nitriles may be hydrolyzed by water in the vpres- 130 to 140 C. preferably under pressure .in a

closed reaction tube. While these methods have been known for the preparation of numerous acids and estersfrom nitriles, it has heretofore 'tained, it is desirable to hold the reaction mix- 7 ture at a temperature within that range for a not been considered that they are applicable .to

the production of esters of acrylic acid.

We have now discovered .a procedure whereby acrylonitrile may be converted into the esters with the saturated, monohydroXy, aliphatic alcohols containing 1 to 3 carbon atoms in the molecule (i. e., into the acrylic acid esters of methanol, ethanol, normal propanol or isopropanol), and whereby this conversion .of the acrylonitrile may be carried out to obtain high yields of the esters and without having to maintain the :materials in process for unduly long periods of time such as to make it impracticable to commercially produce the esters from acrylonitrile.

In producing anacrylic acid ester in accord.- ance with the process of our invention, acrylonitrile is progressively added to water containin an acid. About 1 mol or more of water is present for every 1 mol acrylonitrile added thereto and suflicient acid is added to the water to maintain the reaction mixture acidic throughout the reaction of the water and acrylonitrile.- The acidified water is maintained at temperatures within the range 50 to 120 C., preferably within the range 70 to 100 C., throughout the period of addition thereto of'the acrylonitrile to cause the acrylonitrileand water to undergo a preliminary reaction forming an acrylonitrile derivative. This derivative is heated with methanol, ethanol or .a

propanol, preferably in amount in excess of that stoichiometrically required for formation of ester from the acrylonitrile introduced into the reaction mixture, in the presence of an acid in amount sufficient to maintain the alcoholic reaction mixture acidic, andthe resulting ,ester of acrylicacid is distilled from the reaction mixture.

In the first step of our process, the .rate of .addition of the acrylonitrile to the reaction mixture should be correlated with the temperature at acrylonitrile reacts with the water substantially as fastas it is added to the reaction mixture. Thus, when operating at lower temperatures'in the above range, the acrylonitrile should be progressively added at a slow rate, whereas at higher temperatures which promote more rapid reaction of the acrylonitrile and water, the hitrile may be more ralpidly added to the water containing acid. After addition of the acrylonitrile it is also preferred to hold the reaction mixture to which the reactants have ,been added in the desired proportions for a period of time to insure substantially complete preliminary reaction of the nitrile and water- For example, when areaction temperature of 80 to 90 C. is mainperiod of, for example, about one hour after all of the acrylonitrile has been added. The following table is illustrative of suitable temperatures and times ;for carrying out this first step of the process with'l mol sulfuric acid present for every 1 mol acrylonitrile, but it should be understood that the conditions set forth in the table neednot be rigidly adhered to. There is a considerable latitude in the minimum time for the various temperatures and the time will also depend upon the acid concentration in the water to which the acrylonitrile is added. The maximum time for mixing the acrylonitrile and water is limited only by the (progressive loss of reactants through decomposition or other reactions which may occur when the materials are heated for unduly long periods. In this table, column (1) shows the temperature at which the reactants are heated. Columns (2) and v( 3) respectively, show the suit able times (in hours) for the periods during which the acrylonitrile is progressivelyadded .to

the water (column (2),) and the resulting ,mixture is heated (column (3) )z 60 o 5 1 6040 o 2.5- 1 -soo 1.5 .1 90 o 1 1 (JO-C 0.5 0.5

The acid serves as a catalyst to promote, the reaction of the acrylonitrile and water. For this purpose any of the strong mineral acids such as sulfuric acid, hydrochloric or phosphoric acids, or the acidic organic derivatives of the strong mineral acids such as thesulfonic acids, e. g."be n-* zene sulfonic acid or naphthalene sulfonic acid, may be used. The use of acids to catalyze the hydration of nitriles to acids and the esterification reactions of organic acids with alcohols is known, and any acid used for those purposes may be employed in carrying out our process. In the first step of our process the acid also may serve to neutralize free ammonia which may be formed by the reaction. Widely different concentrations of the acid are effective to promote the reaction of the acrylonitrile and water. Sulfuric acid is preferred, and it is preferred that about 1 mol sulfuric acid be added to the reaction mixture for every 1 mol of acrylonitrile added thereto.

This first step of our process,whereby a, preliminary reaction of the acrylonitrile and water is caused to occur with progressive addition of the acrylonitrile to the reaction mixture and without high concentrations of acrylonitrile building up in the reaction mixtures, is important to the successful operation of our process for the production of acrylic acid esters. Acrylonitrile and reaction products thereof strongly tend to polymerize and th conditions with respect to acidity and elevated temperature at which the acrylonitrile and water are reacted in this first step of our process favor such polymerization. The high heat evolution occurring when polymerization takes place causes a rapid rise in temperature and an almost explosive reaction. The conditions under which the abovedescribed first step of our process are carried out, however, prevent substantial amounts of the acrylonitrile polymerizing and prevent loss of hydroquinone, ptert.-butylcatechol or any of the other materials known to inhibit polymerization of acrylic compounds. 1% to 5% of these inhibitors are preferably added to the acrylonitrile before its addition to the reaction mixture, and smaller proportions of inhibitor to acrylonitrile are also effective aids in preventing polymerization in the first step of our process. More than 5% based on the weight of acrylonitrile may be employed, but the effect of such larger amounts of inhibitor generally does not appear to compensate for the increased cost of providing the higher concentrations of inhibitor. Instead of adding the inhibitor to the acrylonitrile before introducing the latter into the reaction mixture, the inhibitor may b added directly to the reaction mixture before or simultaneously with the addition of the acrylonitrile. It is also known that in the manufacture of acrylonitrile amino compounds may be formed and, when left in the acrylonitrile product, serve to inhibit its polymerization. An acrylonitrile product containing an inhibitor may be used in carrying out our process without addition of inhibitor thereto.

' The preliminary reaction of the acrylonitrile and water in the first step of our process may formacrylic acid or acrylamide, deepnding upon the proportions of water and acrylonitrile which ar present in the reaction mixture. With about 4 water in amount such that there is at least, but not substantially more than, 1 mol water for every 1 mol acrylonitrile added thereto. After mixing these proportions of the acrylonitrile and water before heating the mixture for a further period of time as described above, additional water may be added to the reaction mixture. When, as described hereinafter, the acrylonitrile is to be converted into acrylic acid and this acid recovered and reacted with an alcohol to form the ester, 3 to 10 or more mols water (preferably about '7 mols water) are thus added to the reaction mixture and the mixture heated for a period of time to complete the hydrolysis to the acid before the acrylic acid is recovered from the reaction mixture. It is preferred, however, to employ for reaction with the acrylonitrile not substantially more than 1 mol water, and then, without further addition of water except that incidentally present in the alcohol. used in the second step of our process, to add to the resulting reaction mixture the alcohol which is reacted with the acrylonitrile derivative to form the desired ester of acrylonitrile.

The second step of our process involves the reaction of an alcohol with either or both of these derivatives of the acrylonitrile. Similar procedures may be employed for carrying out the second step of th process whether acrylamide or acrylic acid is the product of the first step. However, when the acrylonitrile first has been converted to acrylic acid, the second step of our process may be modified, as hereinafter described, to recover the acrylic acid from the reaction product of the first step and then treat this acid to esterify it.

The acrylonitrile derivative formed in the first step of the process is reacted with a lower alcohol; i. e., methanol, ethanol or a propanol by heating the derivative with the alcohol, preferably in excess over that required stoichiometrically for formation of the acrylic acid ester, in the presence of an acid. The acids heretofore described as suitable for use in the first step of our process are also suitable for this second step. We prefer to employ in the second step an acidic sulfur-oxygen esterification catalyst. Acidic compounds of this type include sulfuric acid and compounds such as p-toluenesulfonic acid. When a volatile acid such as hydrochloric acid is used, it is preferred to neutralize with an alkali such as sodium hydroxide or carbonate any excess acid present in the reaction mixture after the esterification of the acrylonitrile derivative and before distilling the resulting ester of acrylic acid from the reaction mixture.

It is preferred to heat the alcoholic reaction mixture for a period long enoughto establish substantial equilibrium conditions with respect to formation of the ester before the latter product is distilled from the reaction mixture. The heating of the reaction mixture is preferably carried out under reflux, thus maintaining the temperature as high as feasible under atmospheric pressure without boiling off constituents of the reaction mixture. Lower temperatures may be employed but will generally require a longer pc- 1 mol water per mol of acrylonitrile, acrylamide liminary reaction of the acrylonitrile and water by progressively adding the acrylonitrile to the riod of heating to come to equilibrium and higher temperatures will require operations under pressures above atmospheric, usually without any compensating advantages. By heating the acrylonitrile derivative and alcohol, an ester of acrylic acid is formed and may be distilled over from the reaction mixture.

As in the case of the first step of our process,

polymerization inhibitors should be present in the heated reaction mixture. The same inhibitors effective in the first step of the reaction are effective in this second step and similar amounts are effective to inhibit polymerization in both steps, e. g. 1% to of inhibitor based on the weight of acrylonitrile derivatives present in the reaction mixture treated in the second step of the process.

As pointed out above, it is preferred in carrying out our process to employ in the first step of the process in which acrylonitrile is reacted with water about 1 mol water for every 1 mol acrylonitrile, then to add alcohol to the resulting reaction product, and after heating the mixture to distill off the resulting acrylic acid ester. In this manner of working the two steps of the process are carried out in sequence without-removing any intermediate product from the reaction mixture. The amount of water employed in this procedure may be increased to about 2 mols per mol of acrylonitrileand the resulting reaction mixture treated with alcohol to produce the acrylic acid ester in high yields. When, however, more than this amount of water is used, e. g. about 4 or more mols of water are employed for reaction with the acrylonitrile, it is preferred that the acrylic acid formed under these condition be recovered from the reaction product of the first step. The recovered acrylic acid is then reacted with alcohol to esterify it rather than the acrylic acid being esterified in admixture with the excess water present in the reaction product of the first step of the process, since this excess water would adversely affect the esterification reaction.

The following examples for the production of methyl acrylate from acrylonitrile and methanol are illustrative of our invention. The invention, however, is not limited to the specific procedures of these examples. Particularly, it is not limited to the use of methanol and production of methyl acrylate. Any of the saturated, monohydroxy, aliphatic alcohols containing 3 or less carbon atoms in the molecule may be employed in place of the methanol to form the corresponding esters. Thus, ethanol or normal or isoprop-anol may be used in place of the methanol of these examples without making any other change in the procedural steps of the examples.

Example 1.A mixture of sulfuric acid and water containing 1 mol of H2SO4 for every 1 mol of water is prepared and heated to a temperature of 80 to 96 C. Acrylonitrile containing 5% p-tert.-butylcatechol is slowly added toand dispersed in the sulfuric acid-water mixture while maintaining its temperature in the range 80-90 C. Over a period of on hour 1 mol acrylonitrile is introduced into the reaction mixture for every 1 mol of water present therein. After addition of the acrylonitrile is completed, the reaction mixture is held at temperatures in the range 80-90 C. for an additional period of about one hour. Seven to eight mols of methanol for every 1 mol of the acrylonitrile employed are then added to the reaction mixture and the mixture heated under a reflux condenser for a period of four hours, following which a methanol-methyl acrylate distillate is distilled off from the reaction mixture. The methyl acrylate in the distillate corresponds to about a 73-77 mol percent yield of methyl acrylate based on the acrylonitrile fed to the process.

' A principal by-product of this process, methylbeta-methoxypropionate, may be recovered from the distillation residue by extraction withether 6 and may be converted into methyl acrylate in known manner. For example, the methyl-betamethoxypropionate is heated with phosphorus pentoxide at about 150-170 C. or is passed in the vapor phase at temperatures of 320-380 C. in contact with an activated alumina catalyst. The

' total yields of methyl acrylate obtained from the acrylonitrile may thus be increased to about The use of a smaller proportion of sulfuric acid in the reaction mixture reduces somewhat the yields of methyl acrylate. For example, employing a half mol of sulfuric acid for every 1 mol of water and 1 mol acrylonitrile, other conditions being essentially the same as described above,'resulted in the recovery of a 61% yield of methyl acrylate as a distillate with methanol (not including the additional methyl acrylate which might be obtained by recovering the by-product methylbeta-methoxypropionate and converting it to methyl acrylate).

Reducing the amount of methanol employed in the second step of this procedure also tends to reduce the yields of methyl acrylate. For example, employing 5-6 mols methanol for every 1 mol acrylonitrile, yields of 70 %-73% methyl acrylate recovered directly by distilling the reaction mixture containing methanol were obtained. With a further reduction in the amount of methanol to 3 mols for every 1 mol of acrylonitrile, a yield of about 66% methyl acrylate was obtained. These yields of methyl acrylate may be increased by recovering the by-product methyl-beta-methoxypropionate and treating it as described above.

lircmzple 2.A mixture of sulfuric acid and water containing 1 mol H2804 for every 1 mol H2O is prepared, heated to a temperature in the range 70100 C. and acrylonitrile containing p-tert.- butylcatechol (5%) slowly run into the acid over a period of about one hour as in the initial step of the process of Example 1 above. One mol of the acrylonitrile is added for every 1 mol of water. After holding the reaction mixture at a temperature within the above range for an additional period of one hour, an additional 7-9 mols of water for every 1 mol of acrylonitrile are added and the mixture is refluxed under a reflux oondenser for about four hours, before taking over an aqueous distillate containing acrylic acid. Yields of acrylic acid in the form of this aqueous solution of 80-85% have been obtained based on the initial acrylonitrile.

The aqueous distillate is extracted with chloroform to recover acrylic acid separate from the water. The chloroform is evaporated from the acrylic acid. About 4% p-tert.-butylcatechol is added to the acrylic acid to inhibit its polymerization. There is also added sulfuric acid or p-toluenesulfonic acid to act as catalyst for the esterification reaction of the acrylic acid and an alcohol, e. g. about 1 gram of 96% sulfuric acid for every 72 grams acrylic acid to which 64 grams of methyl alcohol are to be added or about 1 gram of p-toluenesulfonic acid mono-hydrate for every 72 grams acrylic acid to which 94 grams methyl alcohol are to be added. This corresponds to about 0.7% sulfuric acid or about 0.6% p-toluenesulfonic acid, respectively, based on the total reaction mixture of acrylic acid and alcohol. About 0.5% to 2% (weight percent) of acid catalyst based on total reaction mixture (acrylic acid and alcohol to be reacted therewith and any water incidentally added) provides a suitable concentration ofcatalyst for the esterification of acrylic acid. The acid containing the inhibitor and es terification catalyst is heated to about 85 C. and methanol is dropped in.

As the methanol is added, the temperature of the reaction mixture is gradually increased to distill out a mixture of methanol and methyl acrylate as the latter is formed by esterification of the acrylic acid. The total amount of methyl alcohol added is as stated in the preceding paragraph. Towards the end of the reaction the temperature reaches 130 C. An 85 mol percent yield of methyl acrylate was obtained by this procedure, based on the acrylic acid subjected to the esterification treatment. 7

The procedures of the foregoing two examples give methyl acrylate in the form of solutions in methanol which may be treated to recover the methyl acrylate separate from the methanol. Methyl acrylate and methanol form a minimum boiling azeotrope. Accordingly, fractional distillation of the solution of methyl acrylate in methanol does not serve to completely separate the ester from the alcohol but rather yields distillates containing approximately equal proportions of the ester and methanol. A method we have found particularly advantageous for separating the ester and methanol involves addition to the mixture of these two materials (either as initially recovered in the above-described process as distillate in esterifying the acrylic acid or from an ester-methanol fraction recovered by redistilling this initial product) of a compound which forms with the methanol an azeotrope having a lower boiling point than the methyl acrylatemethanol azeotrope boiling at about 6263 C. By distilling the ester-alcohol solution in the presence of such added compound, the methanol is distilled over with the added compound, separated irom the methyl acrylate which remains behind in the residue of this distillation.

As a specific example of this method of recovering the methyl acrylate, the distillate obtained in esterifying acrylic acid by the procedure of Example 2 above is fractionated to recover a fraction containing about equal proportions of methyl acrylate and methanol. To this fraction sufiicient neohexane is added to make the methanol to neohexane ratio about 126 By fractionally distilling the resulting mixture the methanol and neohexane (2,2-dimethyl butane) are carried over as distillate, leaving methyl acrylate in the residue of the distillation separated from the methanol. This residue may be fractionally distill d and a relatively pure methyl acrylate fraction recovered in this final distillation.

In general, hydrocarbons having boiling points in the neighborhood of the boiling points of the alcohol to be separated from the ester may be used in this azeotropic distillation. Preferably a hydrocarbon boiling no higher than and within about 30 C. of the boiling point of the alcohol, is employed to separate the methyl, ethyl or propyl acrylates from the corresponding alcohols.

In the examples for carrying out our process described above, the acrylonitrile is added to a body of acidified water until the desired amount of acrylonitrile for reaction with the water initially present has been added. This is a batch operation, with the reaction medium progressively changing from essentially a body of acidifled water to a body containing but a small proportion of water dispersed in the reaction product of the water and acrylonitrile. This batch procedure may be modified to continuously introduce both waterand acrylonitrile into a body or pool of'their reaction product which thus serves as a medium in which the Water and acrylonitrile react and from which reaction product is continuously withdrawn. At least one mol of water is introduced into this body of reaction product i or every one mol acrylonitrile added thereto and preferably asomewhat greater proportion of water to acrylonitrile is introduced in order to maintain present some excess water to promote reaction of the nitrile as it is progressively added to the pool. The body of reaction product and water added thereto in operating in this manner is continuously maintained at the aforedescribed temperatures in the range 50 to 120 C.

- The rate of addition of water and acrylonitrile to the pool of reaction product serving as a reaction medium and withdrawal of reaction product therefrom is so correlated with the volume of the pool that the time the Water and acrylonitrile remain in the pool is sufficient for substantially complete reaction of the acrylonitrile as it is progressively added to the water introduced into and present in the pool. The rate of addi tion of the acrylonitrile is such that it reacts with the water substantially as fast as the acrylonitrile is added to the pool so that no high concentration of unreacted acrylonitrile is built up therein.

We claim:

1, The process for producing an ester of acrylic acid and a saturated, monohydroxy, aliphatic alcohol containing 1 to 3 carbon atoms in the molecule which comprises maintaining a solution of an acid and water at temperatures within the range of 70 to 0., progressively adding to said solution acrylonitrile in amount corresponding to substantially 1 mol acrylonitrile for every 1 to 2 mols water and at a rate such that the acrylonitrile chemically reacts with the water substantially as fast as it is added to said wateracid solution maintained at the aforesaid temperatures, said solution containing an inhibitor of polymerization of acrylic compounds, heating the reaction product of the acrylonitrile and water with a stoichi'ometric excess or" a saturated,

monchydroxy, aliphatic alcohol containing 1 to 3 carbon atoms in the molecule in the presence of an acid which catalyzes the esterification reaction of an alcohol and an organic acid and distilling the resulting ester of acrylic acid and excess alcohol from the reaction mixture.

2. The process for producing an ester of acrylic acid and a saturated, monohydroxy, aliphatic alcohol containing 1 to 3 carbon atoms in the molecule which comprises maintaining a solution of sulfuric acid and water at temperatures within the range of 50 to C., progressively adding to said solution substantially 1 mol acrylonitrile for every 1 to 2 mols water at a rate such that the acrylonitrile chemically reacts with the water substantially as fast as it is added to said water-sulfuric acid solution at the aforesaid temperatures, said solution containing an inhibitor of polymerization of acrylic compounds, adding to the resulting solution containing reaction prod-. ucts of the acrylonitrile and water a saturated, monohydroxy, aliphatic alcohol containing 1 to 3 carbon atoms in the molecule, heating the mixture in the presence of an acid which catalyzes the esterification reaction of an alcohol and an organic acid to esterify said reaction product. and recovering from the heated mixture the ester of acrylic acid and said alcohol formed by esterification of said reaction products of acrylonitrile.

3'. The process for producing an'ester ofacrylic.

acid and a saturated, monohydroxy, aliphatic alcoholcontaining 1 to 3 carbon atoms in the molecule which comprises maintaininga solution of an acid and .:water at-t'emperatures within the range of 70 to 100 C., progressivelyadding to said solution acrylonitrile ,at'a rate such that the acrylonitrile chemically reacts with the water substantially as fast as'it is aded to'sai'd: wateracid solution at the-aforesaid temperatures'and in amount such that there'is in. thegsolution at least but not substantially more than 1 -mol water for every 1 mol acrylonitrile added there-, to, said solution containing an inhibitor of polymerization of acrylic compounds, adding to the resulting solution, containing'reaction products of the acrylonitrileand water a saturated, monohydroxy, aliphaticlalCohol containing 1 to 3 carbon atoms in the molecule, heating the mixture in the presence of an acidwhichcatalyzes the esterification reaction of an alcohol and an organic acid to esterify said reaction product, and

distilling from the heated mixture the esterigof acrylic acid and saidalcohol formed by esterification of .said react-ionproducts of acrylonitrile- 4. The process for. producing an .ester of acrylic j acid and a sat.urated, monohydroxy, aliphatic alcohol containing 1 to 3 carbon atomsin the molecule which comprises maintaining a soluv tion of sulfuric acid and water at temperatures within the range of 70 to 100 C., progressivelyv adding to said solution substantially 1 mol acrylonitrile for every 1 mol water at a rate such that the acrylonitrile chemically reacts with the water substantially as fast as it is added to said watersulfuric acid solution at the aforesaid temperatures, said solution containing an inhibitor of polymerization of acrylic compounds, adding tothe resulting solution containing reaction products of the acrylonitrile and water a stoichiometric excess of a saturated, monohydroxy, aliphatic alcohol containing 1 to 3 carbon atoms in the molecule, heating the mixture in the presence 10 every 1. mol-watensaidsolution containing an acrylonitrile polymerization inhibitor, maintainin the reaction mixture after addition thereto of the acrylonitrile at temperatures in'the afore said itemperature jrangelforabout one hour, adding tolthe resulting solution containing the reaction product of; the acrylonitrile andwater a stoichiometric excess of t methanol, boiling the mixture in the presenc'eiofsulfuric acid to esterify the reaction product, of the acrylonitrile, and

water,'and distilling fromthe thus heated-mix.- ture the resulting ester of acrylic acid and methanol r v V v'7. The process for'producing methyl acrylate which comprises maintaining a solution of an acid and waterattemperatures within the range 0159703? to: 100" C.,?progressively adding to said solution substantially'l-mol acrylonitrile for every 1- moltwatcriata'rate'such that the acrylonitrile chemically reacts with the water substantially as fastt'as it is added to said water-acid solution at the aforesaid temperatures, said solutioncontaining an inhibitor, of polymerization of acrylic compounds, maintaining the reaction mixture afteraddition theretoiof theacrylonitrile at-tem-.

peratures in the aforesaid temperature range untilcompletion oil'the'reaction of the acrylonitrile and water, adding to the resulting solution containing the reaction product of the acrylonitrile and Water a stoichiometric excess of methanol, heating the mixture inthe presence of an acid which catalyzes the esterification reaction of an alcohol and an organic acid, distilling fromthe heatedmixture the resulting methyl acrylate together with excess methanol,

recovering by-product methyl-beta-methoxypropionate from the residue of the distillation and converting said by-product into methyl acrylate.

8. The process for producing methyl acrylate which comprises maintaining a solution of an of an acid which catalyzes the esterification reaction of an alcohol and an organic acid to esterify said reaction product, and distilling from the heated mixture the resulting ester of acrylic acid together with excess alcohol present therein.

5. The process for producing methyl acrylate which comprises maintaining a solution containing a substantially equal mol ratio of sulfuric acid and water at temperatures within the range of 70 to 100 C., progressively adding. to said solution substantially 1 mol acrylonitrile for every 1 mol water at a rate such that the acrylonitrile chemically reacts with the water substantially as fast as it is added to said water-sulfuric acid solution at the aforesaid temperatures; said solution containing an inhibitor of polymerization of acrylic compounds, adding to the resulting solution containing reaction products 'of the acrylonitrile and water a stoichiometric excess of methanol, heating the mixture in the presence of an acid which catalyzes the esterification reaction of an alcohol and an organic acid to esterify said reaction product, and distilling from the heated mixture a mixture of methanol and methyl acrylate. i

6. The process for producing methylacrylate which, comprises maintaining a solution conacid and water at temperatures within the range of to 100 C., progressively adding to'said solution acrylonitrile at a rate such that the acrylonitrile chemically reacts with the water substantially as fast as it is added to said wateracid solution at the aforesaid temperatures and in amount such that there is in the solution at acid which. catalyzes the esterification reaction of an alcohol and an organic acid, and recovering the resulting methyl acrylate from the reaction mixture. v

9. The process forproducing an ester of acrylic acid and saturated, monohydroxy, aliphatic taining a substantially equal mol ratio of sulfuric acid and water at temperatures within the 1 range of about to about C., progressively n v acrylonitrile chemically reacts with the water" substantially as fast as it is added to said water adding to said solution over aperiod of about one hour substantially 1; mol acrylonitrile for alcohol containing 1 to 3 carbon atoms in the molecule which comprises maintaining a solution of; an acid and water at temperatures within the range of 50 to C., progressively adding tosaid solution acrylonitrile in amount not substantially greater than 1-11101 acrylonitrile for' every'l mol water and at a rate such that the acid solution at the aforesaid temperatures, said solution containing an inhibitor of polymerization of acrylic compounds, heating the reaction product of the acrylonitrile and water with an excess of a saturated, monohydroxy, aliphatic alcoholcontaining 1 to 3 carbon atoms in the molecule in the presence of an acid which catalyzes the esterification reaction of an alcohol and an organic acid, distilling from the reaction mixture the resulting ester of acrylic acid together with excess alcohol, adding to the alcohol-ester mixture a hydrocarbon having a boiling point near that of said alcohol'and forming with the alcohol an azeotrope boiling lower than the azeotrope of the alcohol and ester, and distilling the resulting mixture, thereby distilling over said alcohol as an azeotrope with the hydrocarbon separated from said ester.

10. The process for producing an ester of acrylic acid and a saturated monohydroxy aliphatic alcohol containing 1 to 3 carbon atoms in the molecule, which comprises mixing acrylonitrile with an aqueous solution of an acid in proportions not substantially greater than 1 mol acrylonitrile for every 1 mol of water in the aqueous solution and at temperatures within the range 50 to 120 0., said solution also containing an inhibitor of polymerization of acrylic compounds, heating reaction product of said acrylonitrile and Water with a saturated monohydroxy aliphatic alcohol containing 1 to 3 carbon atoms in the molecule in the presence of an acid which catalyzes the esterification reaction of an alcohol and an organic acid, recovering ester o-f acrylic acidfrom the resulting reaction mixture, and in mixing said acrylonitrile and aqueous solution progressively adding the acrylonitrile to the aqueous solution at a rate such that the acrylonitrile chemically reacts with water in the solution substantially as fast as it is added to the solution.

' PAUL F. WILEY.

GLENN A. NES'I'Y. v

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,998,413 Reppe et a1 Apr. 16, 1935 2,026,894 Hill 1-; Jan. '7, 1936 2,373,464 Dittmar Apr. 10, 1945 2,416,756 Jilk Mar. 4, 1947 

1. THE PROCESS FOR PRODUCING AN ESTER OF ACRYLIC ACID AND A SATURATED, MONOHYDROXY, ALIPHATIC ALCOHOL CONTAINING 1 TO 3 CARBON ATOMS IN THE MOLECULE WHICH COMPRISES MAINTAINING A SOLUTION OF AN ACID AND WATER AT TEMPERATURES WITHIN THE RANGE OF 70* TO 100*C., PROGRESSIVELY ADDING TO SAID SOLUTION ACRYLONITRILE IN AMOUNT CORRESPONDING TO SUBSTANTIALLY 1 MOL ACRYLONITRILE FOR EVERY 1 TO 2 MOLS WATER AND AT A RATE SUCH THAT THE ACRYLONITRILE CHEMICALLY REACTS WITH THE WATER SUBSTANTIALLY AS FAST AS IT IS ADDED TO SAID WATERACID SOLUTION MAINTAINED AT THE AFORESAID TEMPERATURES, SAID SOLUTION CONTAINING AN INHIBITOR OF POLYMERIZATION OF ACRYLIC COMPOUNDS, HEATING THE REACTION PRODUCT OF THE ACRYLONITRILE AND WATER WITH A STOICHIOMETRIC EXCESS OF A SATURATED, MONOHYDROXY, ALIPHATIC ALCOHOL CONTAINING 1 TO 3 CARBON ATOMS IN THE MOLECULE IN THE PRESENCE OF AN ACID WHICH CATALYZES THE ESTERIFICATION REACTION OF AN ALCOHOL AND AN ORGANIC ACID AND DISTILLING THE RESULTING ESTER OF ACRYLIC ACID AND EXCESS ALCOHOL FROM THE REACTION MIXTURE. 